(a) Field of the Invention
The present invention relates to a transmission apparatus, a reception apparatus, a transmission method, and a reception method of a wireless communication system.
(b) Description of the Related Art
When a wireless communication system is designed, there is a growing demand for high data communication speed, realization of low power operation, and good communication performance. Accordingly, the three demands need to be sufficiently taken into consideration when a method of processing signals in a transmission apparatus and a reception apparatus of a wireless communication system is selected.
Meanwhile, to maintain precise timing synchronization in a wireless communication system, a method of reducing a frequency offset between a transmission apparatus and a reception apparatus using a high precision crystal oscillator can be used. However, with a communication system, such as a Wireless Body Area Network (WBAN) for wireless communication between an implant device within the human body and a device outside the human body, is not easy to adopt a precise crystal oscillator because it has to be implemented with an ultra-small size and low power operation.
Further, in wireless communication with a synchronization method, the problem of a frequency offset occurring when data are demodulated can be solved by providing a pilot channel for synchronization acquisition and restoring an accurate frequency by estimating a frequency and a phase offset using a received pilot signal. The performance of such a synchronization reception method is greatly changed depending on how accurately the frequency and the restored phase offset are.
In packet-based wireless communications, such as a Wireless Personal Area Network (WPAN) and the WBAN, a method of estimating and compensating for a frequency error using a preamble is used because it is difficult to additionally support the pilot channel. However, in a reception method estimating synchronization using the preamble, a difference between a frequency offset that is actually applied and an estimated frequency offset generates a remaining frequency offset, thereby degrading the performance of a receiver.
A differential modulation/demodulation method can be used to implement a receiver in an asynchronization reception method performing modulation using a phase difference between symbols and performing demodulation using a phase difference between a previous symbol and a current symbol. Accordingly, the differential modulation/demodulation method can greatly reduce the influence of performance degradation on a change in the frequency offset occurring in the synchronization reception method. Further, the differential modulation/demodulation method is robust to a phase shift of a small range occurring between neighboring symbols, and it can reduce the effect of a phase noise. Moreover, an asynchronous receiver using differential demodulation is advantageous in that it can be simply realized and can greatly reduce complexity because additional circuits for channel estimation and compensation are not required.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.